Re: [PATCH v3 3/7] i2c: aspeed: Fix unhandled Tx done with NAK

[Quan Nguyen]

On 20/05/2021 18:28, Ryan Chen wrote:
> > -----Original Message-----
> > From: Joel Stanley <joel@xxxxxxxxx>
> > Sent: Thursday, May 20, 2021 7:29 AM
> > To: Quan Nguyen <quan@xxxxxxxxxxxxxxxxxxxxxx>; Ryan Chen
> > <ryan_chen@xxxxxxxxxxxxxx>
> > Cc: Corey Minyard <minyard@xxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>;
> > Andrew Jeffery <andrew@xxxxxxxx>; Brendan Higgins
> > <brendanhiggins@xxxxxxxxxx>; Benjamin Herrenschmidt
> > <benh@xxxxxxxxxxxxxxxxxxx>; Wolfram Sang <wsa@xxxxxxxxxx>; Philipp Zabel
> > <p.zabel@xxxxxxxxxxxxxx>; openipmi-developer@xxxxxxxxxxxxxxxxxxxxx;
> > devicetree <devicetree@xxxxxxxxxxxxxxx>; Linux ARM
> > <linux-arm-kernel@xxxxxxxxxxxxxxxxxxx>; linux-aspeed
> > <linux-aspeed@xxxxxxxxxxxxxxxx>; Linux Kernel Mailing List
> > <linux-kernel@xxxxxxxxxxxxxxx>; linux-i2c@xxxxxxxxxxxxxxx; Open Source
> > Submission <patches@xxxxxxxxxxxxxxxxxxx>; Phong Vo
> > <phong@xxxxxxxxxxxxxxxxxxxxxx>; Thang Q . Nguyen
> > <thang@xxxxxxxxxxxxxxxxxxxxxx>; OpenBMC Maillist
> > <openbmc@xxxxxxxxxxxxxxxx>
> > Subject: Re: [PATCH v3 3/7] i2c: aspeed: Fix unhandled Tx done with NAK
> >
> > Ryan, can you please review this change?
> >
> > On Wed, 19 May 2021 at 07:50, Quan Nguyen
> > <quan@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> > > It is observed that in normal condition, when the last byte sent by
> > > slave, the Tx Done with NAK irq will raise.
> > > But it is also observed that sometimes master issues next transaction
> > > too quick while the slave irq handler is not yet invoked and Tx Done
> > > with NAK irq of last byte of previous READ PROCESSED was not ack'ed.
> > > This Tx Done with NAK irq is raised together with the Slave Match and
> > > Rx Done irq of the next coming transaction from master.
> > > Unfortunately, the current slave irq handler handles the Slave Match
> > > and Rx Done only in higher priority and ignore the Tx Done with NAK,
> > > causing the complain as below:
> > > "aspeed-i2c-bus 1e78a040.i2c-bus: irq handled != irq. expected
> > > 0x00000086, but was 0x00000084"
> > >
> > > This commit handles this case by emitting a Slave Stop event for the
> > > Tx Done with NAK before processing Slave Match and Rx Done for the
> > > coming transaction from master.
> >
> > It sounds like this patch is independent of the rest of the series, and can go in
> > on it's own. Please send it separately to the i2c maintainers and add a suitable
> > Fixes line, such as:
> >
> >    Fixes: f9eb91350bb2 ("i2c: aspeed: added slave support for Aspeed I2C
> > driver")
> >
> > > Signed-off-by: Quan Nguyen <quan@xxxxxxxxxxxxxxxxxxxxxx>
> > > ---
> > > v3:
> > >    + First introduce in v3 [Quan]
> > >
> > >   drivers/i2c/busses/i2c-aspeed.c | 5 +++++
> > >   1 file changed, 5 insertions(+)
> > >
> > > diff --git a/drivers/i2c/busses/i2c-aspeed.c
> > > b/drivers/i2c/busses/i2c-aspeed.c index 724bf30600d6..3fb37c3f23d4
> > > 100644
> > > --- a/drivers/i2c/busses/i2c-aspeed.c
> > > +++ b/drivers/i2c/busses/i2c-aspeed.c
> > > @@ -254,6 +254,11 @@ static u32 aspeed_i2c_slave_irq(struct
> > > aspeed_i2c_bus *bus, u32 irq_status)
> > >
> > >          /* Slave was requested, restart state machine. */
> > >          if (irq_status & ASPEED_I2CD_INTR_SLAVE_MATCH) {
> >
> > Can you explain why you need to do this handing inside the SLAVE_MATCH
> > case?
> >
> > Could you instead move the TX_NAK handling to be above the SLAVE_MATCH
> > case?
> >
> > > +               if (irq_status & ASPEED_I2CD_INTR_TX_NAK &&
> > > +                   bus->slave_state ==
> > > + ASPEED_I2C_SLAVE_READ_PROCESSED) {
> >
> > Either way, this needs a comment to explain what we're working around.
> >
> > > +                       irq_handled |= ASPEED_I2CD_INTR_TX_NAK;
> > > +                       i2c_slave_event(slave, I2C_SLAVE_STOP,
> > &value);
>
> According the patch assume slave receive TX_NAK will be go to SLAVE_STOP state?
Hi Ryan,

As per my explain in other email, we need to emit one SLAVE_STOP event 
to complete the previous transaction before start processing for the 
next transaction.

- Quan

> > > +               }
> > >                  irq_handled |= ASPEED_I2CD_INTR_SLAVE_MATCH;
> > >                  bus->slave_state = ASPEED_I2C_SLAVE_START;
> > >          }
> > > --
> > > 2.28.0